JP5449358B2 - Reticle, lithographic apparatus, and method of generating a reticle - Google Patents

Description

  [0001] The present invention relates to a patterning device for use in a lithographic apparatus.

  [0002] Lithography is widely recognized as an important process for fabricating integrated circuits (ICs) and other devices and / or structures. A lithographic apparatus is a machine that applies a desired pattern onto a substrate, for example, a target portion of the substrate, used during lithography. During the manufacture of an IC using a lithographic apparatus, a patterning device (also referred to as a mask or a reticle) generates a circuit pattern that is formed on an individual layer in the IC. This pattern can be transferred onto a target portion (eg including part of, one, or more dies) on a substrate (eg a silicon wafer). Usually, the pattern is transferred by imaging onto a radiation-sensitive material (eg, resist) layer provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Manufacturing different layers of an IC often requires imaging different patterns on different layers with different reticles. Therefore, it is necessary to replace the reticle during the lithography process.

  [0003] Existing extreme ultraviolet (EUV) lithographic apparatus has a substrate formed from ultra-low expansion (ULE) glass, a glass ceramic material having a coefficient of thermal expansion that is substantially zero over a wide range of operating temperatures. Incorporate a reflective reticle. The choice of ULE glass as the substrate is based on the coefficient of thermal expansion of ULE glass and the ability to polish the surface of ULE glass to the fine surface conditions required for EUV lithography applications (ie, exhibiting very low roughness and substantial Without defects and substantially flat).

  [0004] In general, existing reflective reticles for EUV lithographic apparatus exhibit a reflectivity of about 70%. Thus, depending on the pattern to be printed, existing reflective reticles can absorb about 30% to 100% of the energy of the incident EUV radiation beam. Such absorption can lead to significant heating of the reticle that can distort the reticle surface regardless of the relatively low coefficient of thermal expansion of the ULE glass substrate, and can cause errors in the projected image.

  [0005] Furthermore, even when the backside of such a reflective reticle is optimally cooled, the absorption of EUV radiation can result in an excessive temperature gradient across the thickness of the reticle having a ULE glass substrate. Such excessive temperature gradients can result from the relatively low thermal conductivity of the ULE glass substrate, which promotes a relatively high thermal resistance within the ULE glass substrate and thus within the reticle. One variation to an existing reticle design that reduces the thermal resistance of the reticle is to thin the ULE glass substrate and hence the reticle. However, this deformation can create difficulties that may not be overcome at most for keeping the patterned surface flat. In addition, such reticles will deviate from accepted industrial thicknesses for EUV reflective reticles (eg, about 6.35 mm ± 0.10 mm).

  [0006] Therefore, there is a need for a reflective reticle for use in EUV lithography applications that substantially reduces or eliminates pattern distortion due to absorption of EUV radiation while maintaining a reticle thickness consistent with industry standards, thereby Substantially eliminate the failure of the system.

  [0007] In one embodiment, the reticle includes an optical layer having a first surface and a second surface. The reticle also includes a substrate having a thermal conductivity substantially greater than that of the optical layer. The conductive layer is disposed between the optical layer and the substrate. The conductive layer is coupled to one or more of (i) the surface of the substrate and (ii) the first surface of the optical layer. For example, the optical layer may be a material having a substantially zero thermal expansion coefficient, the substrate may be a material having a substantially zero thermal expansion coefficient, and the conductive layer may be aluminum.

  [0008] In a further embodiment, a lithographic apparatus includes an illumination system configured to condition a radiation beam, a reticle configured to pattern the radiation beam, and a patterned beam on a target portion of a substrate. A projection system configured to project. The reticle includes an optical layer having a first surface and a second surface. The reticle further includes a substrate having a thermal conductivity substantially greater than that of the optical layer. The conductive layer is disposed between the optical layer and the substrate and is coupled to one or more of (i) the surface of the substrate and (ii) the first surface of the optical layer. For example, the optical layer may be a material having a substantially zero thermal expansion coefficient, the substrate may be a material having a substantially zero thermal expansion coefficient, and the conductive layer may be aluminum.

  [0009] In a further embodiment, a method is provided for producing a reticle that places a conductive material layer on a first surface of an optical layer. The conductive material layer is then bonded to one of (i) the first surface of the intermediate layer or (ii) the surface of the substrate having a thermal conductivity substantially greater than the thermal conductivity of the optical layer.

  [0010] In a further embodiment, a method of manufacturing a reticle for use in an extreme ultraviolet lithography (EUVL) system is provided. The thick substrate is bonded to the thin film multilayer coating to provide an EUVL reticle having a first thermal conductivity that is relatively higher than the second thermal conductivity of the reflective lithographic reticle formed by the single material layer.

  [0011] Further embodiments, features and advantages of the present invention, as well as the structure and operation of the various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.

  [0012] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention, and together with the description, explain the principles of the invention. It serves to allow a trader to create and use the present invention.

FIG. 1A shows a reflective lithographic apparatus. FIG. 1B shows a transmissive lithographic apparatus. [0014] FIG. 2 shows an exemplary EUV lithographic apparatus. [0015] Figure 3 schematically depicts an existing reflective reticle for use in an EUV lithographic apparatus. [0016] FIG. 4A schematically illustrates exemplary reflective reticle features suitable for use in an EUV lithographic apparatus, according to one embodiment of the invention. [0016] FIG. 4B schematically illustrates exemplary reflective reticle features suitable for use in an EUV lithographic apparatus, according to one embodiment of the invention. [0017] FIG. 5A schematically illustrates features of an exemplary reflective reticle suitable for use in an EUV lithographic apparatus, according to a further embodiment of the invention. [0017] FIG. 5B schematically illustrates features of an exemplary reflective reticle suitable for use in an EUV lithographic apparatus, according to a further embodiment of the invention. [0018] FIG. 6 illustrates additional features of the exemplary reflective reticle of FIGS. 4A, 4B, 5A, and 5B. [0019] FIG. 7 illustrates an exemplary method of generating a reflective reticle suitable for use in an EUV lithographic apparatus, according to an embodiment of the invention. [0019] FIG. 8 illustrates an exemplary method of generating a reflective reticle suitable for use in an EUV lithographic apparatus, according to an embodiment of the invention.

  [0020] One or more embodiments of the present invention are described below with reference to the accompanying drawings. In these drawings, like reference numbers may indicate identical or functionally similar elements.

I. Overview
The present invention relates to a reticle that includes a substrate having high thermal conductivity, and more particularly to a substrate for an EUV reflective reticle having high thermal conductivity. This specification discloses one or more embodiments that incorporate the features of this invention. The disclosed embodiment (s) are merely illustrative of the invention. The scope of the invention is not limited to the disclosed embodiment (s). The invention is limited by the appended claims.

  [0022] References herein to the described embodiment (s) and “one embodiment”, “embodiment”, “exemplary embodiment”, etc. are described (one or more). While embodiments of ()) may include particular features, structures, or characteristics, each embodiment does not necessarily include a particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with one embodiment, such feature, structure, or characteristic may be expressed in a different manner, whether explicitly described or not. It is understood that it is within the knowledge of those skilled in the art to perform in the context of the embodiment.

  [0023] Embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented as instructions stored on a machine-readable medium that can be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (eg, a computing device). For example, machine-readable media can be read only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, electrical, optical, acoustic or other forms of propagated signals (eg, carrier waves) , Infrared signals, digital signals, etc.). Further, firmware, software, routines, instructions, etc. may be described herein as performing certain actions. However, such descriptions are for convenience only and such acts are actually the result of a computing device, processor, controller, or other device executing firmware, software, routines, instructions, etc. I want to be recognized.

  [0024] In various embodiments, a reflective reticle suitable for use in an EUV lithographic apparatus includes an optical layer having a coefficient of thermal expansion that is substantially zero over the temperature range at which the reticle is exposed in the EUV lithographic apparatus. . The optical layer includes a first surface with a conductive layer disposed thereon and a second surface that can be polished so as to be substantially flat and substantially free of defects. For example, the optical layer may be formed from ultra low expansion (ULE) titanium silicate glass and the conductive layer may be aluminum.

  [0025] In one embodiment, the substrate is directly coupled to the first surface of the substrate having a coefficient of thermal expansion that is substantially zero over the operating temperature range and a thermal conductivity substantially higher than the thermal conductivity of the optical layer. In one such embodiment, the substrate may be formed from cordierite having a thermal conductivity that is approximately three times greater than the thermal expansion coefficient of ULE glass. The combined substrate and optical layer form a reticle suitable for use in EUV lithography applications.

  [0026] In a further embodiment, the second conductive layer may be disposed on the first surface of the substrate. Further, the first conductive material layer may then be bonded to the first surface of the intermediate layer and the second conductive layer may be bonded to the second surface of the intermediate layer. For example, as described above, the substrate is formed of Cordierite, the intermediate layer is formed of Zerodur, a non-polymorphic inorganic glass ceramic material, and the second conductive layer is aluminum. Also good. In one such embodiment, the combined optical layer, interlayer and substrate form a reticle suitable for use in EUV lithography applications.

  [0027] These reflective reticles substantially reduce or eliminate pattern distortion resulting from the absorption of EUV radiation, as described below in its various embodiments, while reducing the reticle thickness consistent with industry standards. maintain. Thus, these reflective reticles substantially eliminate the obstacles of existing EUV reticle technology.

  [0028] However, before describing such embodiments in more detail, it is beneficial to present an exemplary environment in which embodiments of the present invention may be implemented.

II. Exemplary lithographic environment
A. Exemplary reflective and transmissive lithography systems
[0029] FIGS. 1A and 1B schematically depict a lithographic apparatus 100 and a lithographic apparatus 100 ′, respectively. Each of lithographic apparatus 100 and lithographic apparatus 100 ′ includes an illumination system (illuminator) IL configured to condition a radiation beam B (eg, DUV or EUV radiation) and a patterning device (eg, mask, reticle or dynamic). A support structure (eg, a mask table) MT configured to support the patterning device (MA) and coupled to a first positioner PM configured to accurately position the patterning device MA; and a substrate (eg, A resist table (W), and a substrate table (for example, a wafer table) WT connected to a second positioner PW configured to accurately position the substrate W. The lithographic apparatuses 100 and 100 ′ are configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (eg including one or more dies) C of the substrate W. Also have. In the lithographic apparatus 100, the patterning device MA and the projection system PS are reflective, and in the lithographic apparatus 100 ′, the patterning device MA and the projection system PS are transmissive.

  [0030] The illumination system IL may be a refractive, reflective, magnetic, electromagnetic, electrostatic, or other type of optical component, or the like, to induce, shape, or control the radiation B Various types of optical components, such as any combination of, can be included.

  [0031] The support structure MT is in a manner that depends on the orientation of the patterning device MA, the design of the lithographic apparatus 100 and 100 ', and other conditions such as whether or not the patterning device MA is held in a vacuum environment, The patterning device MA is held. The support structure MT can hold the patterning device MA using mechanical, vacuum, electrostatic or other clamping techniques. The support structure MT may be, for example, a frame or table that can be fixed or movable as required. The support structure MT may ensure that the patterning device is at a desired position, for example with respect to the projection system PS.

  [0032] The term "patterning device" MA is broadly interpreted to refer to any device that can be used to pattern a cross section of the radiation beam B so as to create a pattern in a target portion C of a substrate W. Should be. The pattern applied to the radiation beam B may correspond to a particular functional layer in the device that is created in the target portion C, such as an integrated circuit.

  [0033] The patterning device MA may be transmissive (as in the lithographic apparatus 100 'of FIG. 1B) or reflective (as in the lithographic apparatus 100 of FIG. 1A). Examples of patterning device MA include reticles, masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase shift, and attenuated phase shift, as well as various hybrid mask types. One example of a programmable mirror array uses a matrix array of small mirrors, and each small mirror can be individually tilted to reflect the incoming radiation beam in various directions. The tilted mirror patterns the radiation beam B reflected by the mirror matrix.

  [0034] The term "projection system" PS refers to refractive, reflective, catadioptric, magnetic types that are appropriate for the exposure radiation used or for other factors such as the use of immersion liquid or vacuum. It should be construed broadly to encompass any type of projection system, including electromagnetic, electrostatic and electrostatic optics, or any combination thereof. A vacuum environment may be used for EUV or electron beam radiation. This is because other gases may absorb too much radiation or electrons. Thus, a vacuum environment may be provided to the entire beam path using a vacuum wall and a vacuum pump.

  [0035] Lithographic apparatus 100 and / or lithographic apparatus 100 'may be of a type having two (dual stage) or more substrate tables (and / or two or more mask tables) WT. In such “multi-stage” machines, additional substrate tables WT can be used in parallel, or one or more substrate tables WT can be run while a preliminary process is performed on one or more tables. It can also be used for exposure.

  [0036] Referring to FIGS. 1A and 1B, the illuminator IL receives a radiation beam from a radiation source SO. For example, if the source SO is an excimer laser, the source SO and the lithographic apparatuses 100 and 100 'may be separate components. In such a case, the source SO is not considered to form part of the lithographic apparatus 100 or 100 ', and the radiation beam B is directed from the source SO to the illuminator IL, for example by suitable guidance. Sent using a beam delivery system BD (FIG. 1B) that includes a mirror and / or a beam expander. In other cases the source SO may be an integral part of the lithographic apparatuses 100 and 100 ', for example when the source SO is a mercury lamp. The radiation source SO and the illuminator IL may be referred to as a radiation system, together with a beam delivery system BD if necessary.

  [0037] The illuminator IL may include an adjuster AD (FIG. 1B) for adjusting the angular intensity distribution of the radiation beam. In general, at least the outer and / or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in the illuminator pupil plane can be adjusted. Further, the illuminator IL may include various other components (FIG. 1B) such as an integrator IN and a capacitor CO. If the radiation beam B is adjusted using the illuminator IL, a desired uniformity and intensity distribution can be provided in the cross section of the radiation beam.

  [0038] Referring to FIG. 1A, the radiation beam B is incident on the patterning device (eg, mask) MA, which is held on the support structure (eg, mask table) MT, and is patterned by the patterning device MA. The In the lithographic apparatus 100, the radiation beam B is reflected from the patterning device (eg mask) MA. After reflection from the patterning device (eg mask) MA, the radiation beam B passes through the projection system PS, which focuses the radiation beam B on the target portion C of the substrate W. The substrate table is used, for example, to position various target portions C in the path of the radiation beam B using the second positioner PW and the position sensor IF2 (eg, interferometer device, linear encoder, or capacitive sensor). The WT can be moved accurately. Similarly, the first positioner PM and another position sensor IF1 can be used to accurately position the patterning device (eg mask) MA with respect to the path of the radiation beam B. Patterning device (eg mask) MA and substrate W may be aligned using mask alignment marks M1 and M2 and substrate alignment marks P1 and P2.

  [0039] Referring to FIG. 1B, the radiation beam B is incident on the patterning device (eg, mask MA), which is held on the support structure (eg, mask table MT), and is patterned by the patterning device. . After passing through the mask MA, the radiation beam B passes through the projection system PS, which focuses the radiation beam onto the target portion C of the substrate W. The substrate table is used, for example, to position various target portions C in the path of the radiation beam B using a second positioner PW and a position sensor IF (eg, interferometer device, linear encoder, or capacitive sensor). The WT can be moved accurately. Similarly, the first positioner PM and another position sensor (not explicitly shown in FIG. 1B) are used to emit the mask MA after, for example, mechanical removal of the mask from the mask library or during a scan. It can also be accurately positioned with respect to the path of the beam B.

  [0040] Normally, the movement of the mask table MT can be achieved using a long stroke module (coarse positioning) and a short stroke module (fine positioning) that form part of the first positioner PM. Similarly, movement of the substrate table WT can also be achieved using a long stroke module and a short stroke module that form part of the second positioner PW. In the case of a stepper (as opposed to a scanner) the mask table MT may be connected to a short stroke actuator only, or may be fixed. Mask MA and substrate W may be aligned using mask alignment marks M1 and M2 and substrate alignment marks P1 and P2. In the example, the substrate alignment mark occupies the dedicated target portion, but the substrate alignment mark can also be placed in the space between the target portion (these are known as scribe line alignment marks). Similarly, if a plurality of dies are provided on the mask MA, the mask alignment mark may be placed between the dies.

  [0041] The lithographic apparatuses 100 and 100 'may be used in at least one of the modes described below.

  [0042] In step mode, the entire pattern applied to the radiation beam B is projected onto the target portion C at once (ie, while the support structure (eg, mask table) MT and substrate table WT are essentially stationary) (ie, Single static exposure). Thereafter, the substrate table WT is moved in the X and / or Y direction so that another target portion C can be exposed.

  [0043] 2. In scan mode, the support structure (eg, mask table) MT and substrate table WT are scanned synchronously while a pattern imparted to the radiation beam B is projected onto a target portion C (ie, a single dynamic exposure). ). The speed and direction of the substrate table WT relative to the support structure (eg mask table) MT can be determined by the (reduction) magnification factor and image reversal characteristics of the projection system PS.

  [0044] 3. In another mode, with the programmable patterning device held, the support structure (eg mask table) MT is kept essentially stationary and the substrate table WT is moved or scanned while the radiation beam B is The attached pattern is projected onto the target portion C. A pulsed radiation source SO is employed and the programmable patterning device is updated as necessary after each movement of the substrate table WT or between successive radiation pulses during the scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as described above.

  [0045] Combinations and / or variations on the above described modes of use or entirely different modes of use may also be employed.

  [0046] Although specific reference is made herein to the use of a lithographic apparatus in IC manufacture, the lithographic apparatus described herein is an integrated optical system, a guidance pattern and a detection pattern for a magnetic domain memory, It should be understood that other applications such as the manufacture of flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads and the like may be had. As will be appreciated by those skilled in the art, in such other applications, the terms “wafer” or “die” as used herein are all more general “substrate” or “target” respectively. It may be considered synonymous with the term “part”. The substrate described herein can be used, for example, before or after exposure, such as a track (usually a tool for applying a resist layer to the substrate and developing the exposed resist), a metrology tool, and / or an inspection tool. May be processed. Where applicable, the disclosure herein may be applied to substrate processing tools such as those described above and other substrate processing tools. Further, since the substrate may be processed multiple times, for example, to make a multi-layer IC, the term substrate as used herein may refer to a substrate that already contains multiple processing layers.

  [0047] In a further embodiment, the lithographic apparatus 100 includes an extreme ultraviolet (EUV) source configured to generate an EUV radiation beam for EUV lithography. In general, the EUV source is configured in a radiation system (see below) and the corresponding illumination system is configured to condition the EUV radiation beam of the EUV source.

B. Exemplary EUV lithography apparatus
[0048] Figure 2 schematically depicts an exemplary EUV lithographic apparatus 200 according to one embodiment of the invention. In FIG. 2, the EUV lithographic apparatus 200 includes a radiation system 42, an illumination optics unit 44, and a projection system PS. The radiation system 42 includes a radiation source SO in which a radiation beam can be formed by a discharge plasma. In one embodiment, EUV radiation is generated by a gas or vapor such as Xe gas, Li vapor or Sn vapor, for example, where a very hot plasma is generated to emit radiation in the EUV range of the electromagnetic spectrum. obtain. A very hot plasma can be created by generating an at least partially ionized plasma, for example by discharge. For example, 10 Pa of Xe, Li, Sn vapor, or any other suitable gas or vapor partial pressure may be required for efficient generation of radiation. Radiation emitted by the radiation source SO travels from the radiation source chamber 47 to the collector chamber 48 via a gas barrier or contaminant trap 49 positioned in or behind the opening in the radiation source chamber 47. In one embodiment, the gas barrier 49 may include a channel structure.

  [0049] The collector chamber 48 includes a radiation collector 50 (also referred to as a collection mirror or collector) that may be formed by a grazing incidence collector. The radiation collector 50 has an upstream radiation collector side 50a and a downstream radiation collector side 50b. Radiation that has passed through the collector 50 can be reflected from the grating spectral filter 51 and focused at a virtual source point 52 at an aperture in the collector chamber 48. The radiation collector 50 is well known to those skilled in the art.

  [0050] The radiation beam 56 enters the illumination optical unit 44 from the collection chamber 48 via a normal incidence reflector 53 and 54 onto a reticle or mask (not shown) positioned on the reticle or mask table MT. Reflect on. A patterned beam 57 is formed, which is imaged on a substrate (not shown) supported on a wafer stage or substrate table WT via reflective elements 58 and 59 in the projection system PS. In various embodiments, the illumination optics unit 44 and the projection system PS may include more (or fewer) elements than those shown in FIG. For example, the grating spectral filter 51 may optionally be present depending on the type of lithographic apparatus. Further, in one embodiment, the illumination optics unit 44 and the projection system PS may include more mirrors than those shown in FIG. For example, the projection system PS may incorporate 1-4 reflective elements in addition to the reflective elements 58 and 59. In FIG. 2, reference numeral 180 indicates a space between two reflectors, for example, a space between the reflectors 142 and 143.

  [0051] In one embodiment, the collector mirror 50 may include a normal incidence collector instead of or in addition to the grazing incidence mirror. Furthermore, although the collector mirror 50 is described for a nested collector having reflectors 142, 143, and 146, it is further used herein as an example of a collector.

  Furthermore, a transmission type optical filter may be applied instead of the grating 51 schematically shown in FIG. Optical filters that transmit EUV, as well as optical filters that transmit less UV radiation or even substantially absorb UV radiation, are well known to those skilled in the art. Accordingly, “grating spectral purity filter” is further referred to herein in substantially the same sense as a “spectral purity filter” including a grating or transmission filter. Although not shown in FIG. 2, the EUV transmissive optical filter is, for example, as an additional optical element configured upstream of the collector mirror 50, or as an optical EUV transmissive filter in the illumination unit 44 and / or the projection system PS. May be included.

  [0053] The terms "upstream" and "downstream" with respect to an optical element refer to the position of one or more optical elements that are "optically upstream" and "optically downstream", respectively, of one or more additional optical elements. Show. According to the optical path through which the radiation beam passes through the lithographic apparatus 200, the first optical element closer to the radiation source SO than the second optical element is configured upstream of the second optical element, and the second optical element is configured downstream of the first optical element. The For example, the condensing mirror 50 is configured upstream of the spectral filter 51, while the optical element 53 is configured downstream of the spectral filter 51.

  [0054] All optical elements shown in FIG. 2 (and additional optical elements not shown in the schematic of this embodiment) are susceptible to deposition of contaminants generated by a radiation source SO such as Sn, for example. Sometimes. This is also true for the radiation collector 50, even if a spectral purity filter 51 is present. Accordingly, although a cleaning device may be employed to clean one or more of these optical elements and a cleaning method may be applied to those optical elements, normal incidence reflectors 53 and 54, and reflective elements 58 and 59, or other optical elements such as additional mirrors, gratings, etc. may be applied.

  [0055] The radiation collector 50 may be a grazing incidence collector, and in such embodiments, the collector 50 is aligned along the optical axis O. The radiation source SO or an image thereof may be arranged along the optical axis O. The radiation collector 50 may include reflectors 142, 143 and 146 ("shells"), also known as Wolter-type reflectors, including several Wolter-type reflectors. The reflectors 142, 143 and 146 may be nested and rotationally symmetric about the optical axis O. In FIG. 2, the inner reflector is indicated by reference numeral 142, the intermediate reflector is indicated by reference numeral 143, and the outer reflector is indicated by reference numeral 146. The radiation collector 50 encloses a volume (ie, the volume in the (one or more) outer reflectors 146). Typically, the volume within the outer reflector (s) 146 is closed in the circumferential direction, although there may be small openings.

  [0056] Each of the reflectors 142, 143, and 146 may include a surface at least a portion of which represents a single reflective layer or multiple reflective layers. Accordingly, the reflectors 142, 143 and 146 (or additional reflectors in embodiments of radiation collectors having more than three reflectors or shells) are at least partially designed to reflect and collect EUV radiation from the radiation source SO. And at least some of the reflectors 142, 143 and 146 may not be designed to reflect and collect EUV radiation. For example, at least a portion of the back surface of the reflector is not designed to reflect and collect EUV radiation. An optical filter provided on at least a part of the surface of the cap layer or the reflective layer for protection may be present on the surface of the reflective layer.

  [0057] The radiation collector 50 may be arranged in the vicinity of the radiation source SO or an image of the radiation source SO. Each of the reflectors 142, 143 and 146 may include at least two adjacent reflecting surfaces, and the reflecting surface located farther from the radiation source SO is more reflective than the reflecting surface located closer to the radiation source SO. It is arranged at a small angle with respect to the optical axis O. In this way, the grazing incidence collector 50 is configured to generate an (E) UV radiation beam that propagates along the optical axis O. The at least two reflectors may be arranged substantially coaxially and extend substantially rotationally symmetrical about the optical axis O. It should be understood that the radiation collector 50 may have additional features on the outer surface of the outer reflector 146, or additional features around the outer reflector 146, such as a protective holder or heater.

  [0058] In the embodiments described herein, the terms "lens" and "lens element" may refer to various types of refraction, reflection, magnetic, electromagnetic, and electrostatic optical components, depending on the context. It can refer to any one or a combination of optical components.

  [0059] As used herein, the terms "radiation" and "beam" refer to ultraviolet (UV) (eg, having a wavelength λ of 365, 248, 193, 157, or 126 nm), extreme ultraviolet (EUV or soft). X-rays) (for example, having a wavelength in the range of 5-20 nm, for example having a wavelength of 13.5 nm) or hard X-rays working below 5 nm, as well as all types of electromagnetic Includes radiation. In general, radiation having a wavelength between about 780 and 3000 nm (and above) is considered IR radiation. UV refers to radiation having a wavelength of about 100-400 nm. In lithography, UV also applies to wavelengths that can be generated by mercury discharge lamps, namely G-line 436 nm, H-line 405 nm and / or I-line 365 nm. Vacuum UV or VUV (ie UV absorbed by air) refers to radiation having a wavelength of about 100-200 nm. Deep UV (DUV) typically refers to radiation having a wavelength in the range of 126 nm to 428 nm, and in one embodiment, an excimer laser can produce DUV radiation that is used in a lithographic apparatus. For example, those skilled in the art will appreciate that radiation having a wavelength in the range of 5-20 nm relates to radiation having a particular wavelength band, at least in part in the range of 5-20 nm.

III. Exemplary substrate for EUV reticle having high thermal conductivity
[0060] FIG. 3 schematically illustrates an example of an existing EUV reflective reticle 300 formed from a single layer of substrate material. In FIG. 3, the reticle 300 includes a substrate 302 on which one or more highly reflective materials are disposed to form a reflective layer 304. A pattern (not shown) is formed on the reflective surface 304a of the layer 304 through chemical etching of the patterned layer of resist, or in addition or alternatively, through any other technique apparent to those skilled in the art. May be formed.

  [0061] Existing EUV reflective reticle substrates, such as substrate 302, are optical grade glass, ceramic, glass-ceramic materials, and relatively over a wide range of temperatures, eg, the temperature range at which the substrate is exposed in an EUV lithographic apparatus. Often composed of other materials characterized by a low coefficient of thermal expansion and high modulus. For example, the substrate 302 may be formed from ultra low expansion (ULE) titanium silicate glass as manufactured by Corning, Corning, NY.

  [0062] However, substrates composed of these materials also exhibit relatively low values of thermal conductivity over the temperature range in which the substrate is exposed in an EUV lithographic apparatus. For example, the average thermal conductivity of ULE glass is about 1.31 W / (m- ° C.) at 25 ° C., while the average thermal conductivity of aluminum is about 250 W / (m- ° C.) at 25 ° C. Such a value of thermal conductivity can lead to a relatively large thermal resistance across the thickness of the substrate (ie, the quotient of the thickness of the substrate and its thermal conductivity), thus the uniformity of heat in the substrate. And prevent conduction to peripheral portions of the EUV lithographic apparatus including, but not limited to, one or more devices that support the reticle from the substrate.

  [0063] As noted above, existing EUV reticles absorb between about 30% and 100% of the incident EUV radiation beam. Absorption of EUV radiation by such a reticle can result in local heating of the substrate that cannot diffuse or leave the substrate due to the mechanical properties of the substrate. In such cases, this heating can locally deform the substrate, and therefore the corresponding reflective layer (eg, surface 308a of reflective layer 308 in FIG. 3). In addition, thermally driven distortion of the pattern surface can distort the pattern imparted to the incident radiation beam and cause errors in the image projected onto the substrate by the EUV lithographic apparatus.

  [0064] Generally, existing EUV lithographic apparatus cannot compensate for more than a small amount of error caused in a patterned image due to thermal distortion of the patterning surface. Thus, thermal distortion of both the patterned image and the patterning surface is a factor that limits imaging performance in existing EUV lithographic apparatus. Furthermore, the problem of pattern distortion due to reticle heating can be exacerbated as more energy is supplied to the reflective reticle to meet the increased throughput requirements of volume manufacturing in EUV lithographic apparatus.

  [0065] In one embodiment, the effects of local reticle heating due to radiation absorption can be mitigated by increasing the thermal conductivity of the substrate in the reflective reticle. By increasing the thermal conductivity of the substrate and thereby reducing the thermal resistance of the substrate (of constant thickness), the local heating by absorbed radiation is more evenly distributed in the substrate and from the substrate to the reticle. It can be more efficiently transported to peripheral support devices including but not limited to a chuck or mask table. Thus, an increase in the thermal conductivity of the reticle substrate can substantially reduce or eliminate any induced distortion of the patterning surface and hence the induced error of the patterned image.

  [0066] One suitable substrate material for inclusion in a reflective reticle for an EUV lithographic apparatus includes ceramic materials, cordiers available from a number of suppliers, including but not limited to Tallytown, Hitachi Metals America, Inc., New York. Light. Cordierite has a coefficient of thermal expansion that is substantially zero over the operating temperature range experienced by EUV reticles, while also having a thermal conductivity that is approximately three times greater than existing reticle substrate materials. For example, ULE glass has a thermal conductivity of about 1.31 W / (m- ° C.) at 25 ° C., while the thermal conductivity of cordierite at 25 ° C. is about 3.0 W / (m- ° C.). .

  [0067] However, the microstructure of solid cordierite makes it unsuitable to use materials as substrates in existing reflective reticles. Solid cordierite, when polished, incorporates fine voids that form holes and other defects on the polished cordierite surface. The presence of these surface defects makes it inappropriate to apply a reflective material to form the reflective layer of the reticle, eg, the reflective layer 308 of the reticle 300 of FIG. 3, to the cordierite surface being polished.

  [0068] In one embodiment, microstructural defects that make it inappropriate to use cordierite as a substrate in an existing reflective reticle are obtained by bonding a relatively thin optical material layer to the surface of the cordierite substrate. Can be repaired. In such an embodiment, as shown in FIGS. 4A and 4B, the thin optical layer is processed (eg, polished) and substantially flat without defects indicative of the properties of the cordierite surface being polished. Create a surface. In such embodiments, the optical layer is thin enough to provide a conventional glass surface that provides low thermal resistance while surface polishing, film application, and patterning on top.

  [0069] FIG. 4A is an exploded schematic view of an exemplary reflective reticle 400 suitable for use in a lithographic apparatus, according to one embodiment of the invention. In contrast to existing reflective reticle technology for EUV lithographic apparatus as shown in FIG. 3, reticle 400 includes substrate 402, optical layer 404, and conductive layer 406 disposed between substrate 402 and optical layer 404. including. In such embodiments, the complexity of reticle 400 substantially reduces or eliminates reticle surface distortion due to the absorption of radiation characteristic of existing EUV reflective reticles and the introduction of errors in the patterned image.

  In FIG. 4A, the optical layer 404 has a first surface 404a and a second surface 404b, and the substrate 402 has a first surface 402a and a second surface 402b. In such an embodiment, the conductive layer 406 is disposed between the first surface 404 a of the optical layer 404 and the first surface 402 a of the substrate 402. Further, in one embodiment, the conductive layer 406 may be disposed on the first surface 404a of the optical layer 404.

  [0071] In one embodiment, the conductive layer 406 may be a metal layer, including but not limited to aluminum, a non-metallic conductive material such as graphite, or any combination thereof. Further, in one embodiment, the conductive layer 406 may be deposited on the first surface 404a of the optical layer 404 via any number of deposition techniques that are apparent to those skilled in the art and are suitable for the material. For example, the conductive layer 406 may be disposed on the first surface 404a of the optical layer 404 using sputter deposition or spray deposition. In further embodiments, the conductive layer 406 may be pre-assembled and bonded to the first surface 404a of the optical layer 404 using any additional or alternative technique suitable for the conductive layer 406 and the optical layer 404.

  [0072] FIG. 4B schematically illustrates additional features of the example reticle 400 shown in FIG. 4A. In FIG. 4B, the reticle 400 is formed by bonding the conductive layer 406 disposed on the surface 404 a to the first surface 402 a of the substrate 402 to form the reticle 400. In one embodiment, the conductive layer 406 may be bonded to the first surface 402a using any number of techniques that will be apparent to those skilled in the art including, but not limited to, anodic bonding.

  [0073] In one embodiment, second surface 402b of reticle 400 (and substrate 402) may be supported by a reticle chuck, mask table, or any other device in an EUV lithographic apparatus. In such embodiments, the reticle chuck, mask table or other device can serve as a heat sink for reticle 400, thereby facilitating heat transfer from reticle 400 to various components of the EUV lithographic apparatus. To.

  [0074] In one embodiment, as shown in FIG. 4B, the optical layer 404 is bonded to the substrate 402 or otherwise attached to the substrate 402, whereby the first layer 404a of the optical layer 404 is attached to the substrate 402. Substantially parallel to the first surface 402a. Furthermore, the second surface 404b of the optical layer 404 is also substantially parallel to the first surface 404a, and similarly, the second surface 402b of the substrate 402 is substantially parallel to the first surface 402a. However, the invention is not limited to substrates and optical layers that are combined or otherwise attached in such a configuration. In further embodiments, each of the first and second surfaces of the substrate 402 and the optical layer 404 includes, but is not limited to, those configured at any angle with respect to each other without departing from the spirit or scope of the present invention. Each may be located in any configuration that is not.

  [0075] In one embodiment, as described above, the optical layer 404 may be formed from a material having a coefficient of thermal expansion that is substantially zero over the temperature range experienced by the reticle 400. For example, the optical layer 404 may be formed from ultra low expansion (ULE) titanium silicate glass manufactured by Corning, Corning, NY. In such embodiments, the thickness of the optical layer 404 is selected to provide a surface with sufficient integrity to support polishing and application of the reflective film while maintaining a relatively low thermal resistance. Good. For example, the thickness of the optical layer 404 can be as low as about 0.025 mm, but can range from about 0.1 mm to about 0.5 mm.

  [0076] Further, as described above, the substrate 402 has a coefficient of thermal expansion that is substantially zero over the temperature range and also has a thermal conductivity that is approximately three times greater than the coefficient of thermal expansion of the optical layer. (Eg, cordierite has a thermal conductivity of about 3.0 W / (m- ° C.) at 25 ° C. and ULE glass is about 1.31 3.0 W / (m − at 25 ° C.). C)). In one embodiment, the thickness of the substrate 402 may range from about 5.25 mm to about 6.25 mm.

  [0077] As described above, the reticle 400 can absorb about 30% to 100% of an incident EUV radiation beam when incorporated in an EUV lithographic apparatus. However, in the embodiment of FIGS. 4A and 4B, local heating of the optical layer 404 that may result from the absorption of EUV radiation diffuses quickly or is conducted through the optical layer 404 due to its low thermal resistance, and further conductive. Conducted through layer 406 to substrate 402. Further, since the thermal conductivity of the substrate 402 is substantially higher than that of the substrate of existing EUV reticles, local heating due to absorption of EUV radiation diffuses uniformly into the substrate and passes through the substrate through the EUV. It is quickly dissipated into a reticle chuck, mask table or other structure that supports reticle 400 in the lithographic apparatus. Thus, in contrast to the existing EUV reticle shown in FIG. 3, reticle 400 substantially reduces or reduces any distortion of the reticle surface due to local heating from absorbed EUV radiation, and any pattern errors induced by it. Remove.

  [0078] In the embodiment of FIGS. 4A and 4B, conductive layer 406 is disposed on first surface 404a of optical layer 404, and then conductive layer 406 is coupled to first surface 402a of substrate 402. However, in further embodiments, the intermediate layer of material may further isolate the optical layer 404 from the substrate 402. For example, a substrate formed of cordierite may not have sufficient conductivity to be anodically bonded to the conductive layer 406. In such embodiments, an intermediate layer can be positioned between the substrate 402 and the optical layer 404 to facilitate such anodic bonding.

  [0079] FIG. 5A is an exploded schematic view of an exemplary reflective reticle 500 for use in an EUV lithography system, according to a further embodiment of the invention. In contrast to the embodiment of FIG. 4, reticle 500 includes an intermediate layer 530 that separates substrate 502 from optical layer 504. In such embodiments, the intermediate layer 530 facilitates bonding between the optical layer 504 and the substrate 502.

  [0080] Similar to the embodiment of FIGS. 4A and 4B, the optical layer 504 has a first surface 504a and a second surface 504b. In one embodiment, the second surface 504b is substantially flat and defective through any number of techniques apparent to those skilled in the art including, but not limited to, polishing with various abrasives. It can be processed so as not to have.

  The conductive layer 506 is disposed between the first surface 504a of the optical layer 504 and the first intermediate surface 530a of the intermediate layer 530. In the embodiment of FIG. 5A, the conductive layer 506 is disposed on the first surface 504a. However, the present invention is not limited to such configurations, and in further embodiments, the conductive layer 506 is disposed on the first intermediate surface 530a of the intermediate layer 530 without departing from the spirit or scope of the present invention. It's okay.

  [0082] In such embodiments, the conductive layer 506 may be a metal layer, including but not limited to aluminum, a non-metallic conductive material such as graphite, or any combination thereof. Further, in one embodiment, the conductive layer 506 is deposited on the first surface 504a of the optical layer 504 (or alternatively, the first of the intermediate layer 530) via any number of deposition techniques that are apparent to those skilled in the art and are suitable for the material. 1 on the intermediate surface 530a). For example, the conductive layer 506 may be disposed on the first surface 504a or the first intermediate surface 530a using any sputter deposition, spray deposition or physical vapor deposition techniques.

  [0083] In a further embodiment, the conductive layer 506 may be a pre-assembled layer of conductive material. In such embodiments, the pre-assembled conductive layer 506 is either on the first surface 504a of the optical layer 504 or the first intermediate surface 530a of the intermediate layer 530 that is apparent to those skilled in the art and is suitable for the material. May be combined.

  Furthermore, in contrast to the embodiment of FIGS. 4A and 4B, the second conductive layer 516 is disposed between the intermediate layer 530 and the substrate 502. In the embodiment of FIG. 5A, the second conductive layer 516 is disposed on the first surface 502 a of the substrate 502. However, the present invention is not limited to such a configuration, and in a further embodiment, the conductive layer 516 is disposed on the second intermediate surface 530b of the intermediate layer 530 without departing from the spirit or scope of the present invention. It's okay.

  [0085] In such an embodiment, similar to those described above, the conductive layer 516 may be a metal layer including but not limited to aluminum, a non-metallic conductive material such as graphite, or any combination thereof. . Further, in one embodiment, the conductive layer 516 is deposited on the first surface 502a of the substrate 502 (or alternatively, the second of the intermediate layer 530) via any number of deposition techniques that are apparent to those skilled in the art and are suitable for the material. (On intermediate surface 530b). For example, the conductive layer 516 may be disposed on the first surface 502a or the second intermediate surface 530b using any sputter deposition, spray deposition, or physical vapor deposition technique.

  [0086] FIG. 5B schematically illustrates additional features of the reticle 500 shown in FIG. 5A. In FIG. 5B, reticle 500 first bonds first coupled conductive layer 506 disposed on first surface 504a of optical layer 504 to first intermediate surface 530a of intermediate layer 530, and then first surface of substrate 502. A conductive layer 516 disposed on 502a is formed by bonding to a second intermediate layer 530b of intermediate layer 530. In one embodiment, conductive layer 506 and conductive layer 513 may be anodically coupled to first intermediate surface 530a and second intermediate surface 530b, respectively. However, the present invention is not limited to anodic bonding, and in further embodiments, one or more conductive layers 506 and 516 can be any number of techniques that are apparent to those skilled in the art and are suitable for conductive layers 506 and 516. May be coupled to, or otherwise attached to, each of the corresponding first intermediate surface 530a and second intermediate surface 530b.

  [0087] In one embodiment, the second surface 502b of the substrate 502 (and thus the reticle 500) is supported by a reticle chuck, mask table or any other device configured to support the reticle 500 in an EUV lithographic apparatus. May be. In such embodiments, a reticle chuck, mask table or other device can serve as a heat sink for reticle 400, thereby facilitating heat transfer from reticle 500 to various components of the EUV lithographic apparatus. To.

  [0088] In the embodiment of FIGS. 5A and 5B, first and second surfaces 504a and 504b of optical layer 504, first and second surfaces 502a and 502b of substrate 502, and first intermediate surface 530a of intermediate layer 530, respectively. And each of the second intermediate surfaces 530b are substantially parallel to each other. However, the invention is not limited to substrates and optical layers that are combined or otherwise attached in such a configuration. In a further embodiment, of the first surface 504a and the second surface 504b of the optical layer 504, the first surface 502a and the second surface 502b of the substrate 502, and the first intermediate surface 530a and the second intermediate surface 530b of the intermediate layer 530 One or more of these may be disposed at any angle with respect to any other surface that would be apparent to those skilled in the art and that are suitable for reticle 500 without departing from the spirit or scope of the present invention.

  [0089] In one embodiment, as described above with reference to FIGS. 4A and 4B, optical layer 504 includes an operating temperature range experienced by reticle 500, including but not limited to ultra-low expansion (ULE) titanium silicate glass. May be formed from a material having a coefficient of thermal expansion that is substantially zero over. In such embodiments, the thickness of the optical layer 504 may be selected to maintain a relatively low thermal resistance and provide a surface with sufficient integrity to support polishing. For example, the thickness of the optical layer 504 can be as low as about 0.025 mm, but can range from about 0.1 mm to about 0.5 mm.

  [0090] Further, as described above, the substrate 502 has a coefficient of thermal expansion that is substantially zero over the operating temperature range and also has a thermal conductivity that is approximately three times greater than the coefficient of thermal expansion of the optical layer. (Eg, cordierite has a thermal conductivity of about 3.0 W / (m- ° C.) at 25 ° C. and ULE glass is about 1.31 3.0 W / (m at 25 ° C.). A thermal conductivity of − ° C.). In one embodiment, the thickness of the substrate 502 can range from about 5.25 mm to about 6.25 mm.

  [0091] Further, in the embodiment of FIGS. 5A and 5B, the intermediate layer 530 may be formed from a glass material, a ceramic material, or a glass-ceramic material having a coefficient of thermal expansion that is substantially zero. For example, the intermediate layer 530 may be formed from Zerodur, a non-polymorphic inorganic glass ceramic material manufactured by Schott North America, Elmsford, NY. Further, in one embodiment, the thickness of the intermediate layer 530 may be substantially less than the thickness of the substrate 502 and the thermal resistance of the intermediate layer is substantially equal to or less than the thickness of the optical layer 504. May be selected. For example, the thickness of the intermediate layer formed from zerodure can be as low as about 0.025 mm, but can range from about 0.1 mm to about 0.5 mm.

  [0092] However, the present invention is not limited to an intermediate layer formed from zero-dur, and in a further embodiment, the intermediate layer 530 has suitable mechanical properties (eg, substantially zero heat over the operating temperature range). It may be formed from any number of materials that have a coefficient of expansion) and can facilitate anodic bonding with the optical layer 504 and the substrate 502.

  [0093] As described above, reticle 500, when incorporated in an EUV lithographic apparatus, can absorb about 30% to 100% of an incident EUV radiation beam. However, similar to the embodiment of FIGS. 4A and 4B, any local heating of the optical layer 504 that can result from absorption of EUV radiation diffuses quickly (eg, conducts) through the optical layer due to its low thermal resistance, Further, the light is diffused through the conductive layer 506 to the intermediate layer 530 and then through the second conductive layer 516 to the substrate 502. Furthermore, since the thermal conductivity of the substrate 502 is substantially higher than that of the substrate of existing EUV reticles, local heating of the substrate by absorption of EUV radiation diffuses into the substrate and is within the EUV lithographic apparatus. Dissipated into a reticle chuck, mask table or other structure that supports reticle 500. Therefore, in contrast to the existing EUV reticle shown in FIG. 3, the reticle 500 substantially reduces any distortion of the reticle surface due to localized heating from absorbed EUV radiation, and thus any induced pattern errors. Remove.

  [0094] FIG. 6 schematically illustrates a portion of an exemplary reticle 600 (as shown in FIGS. 4A-4B and 5A-5B) after additional processing and patterning, according to one embodiment of the invention. Shown in In FIG. 6, the optical layer 604 of the reticle 600 has a first surface 604a and a second surface 604b, and a conductive coating 606 is disposed on the first surface 604a. In the embodiment of FIG. 6, the second surface 604b is processed using any of a number of techniques that will be apparent to those skilled in the art to produce a substantially flat surface that is substantially free of defects. In such an embodiment, a material layer 608 that is highly reflective to EUV radiation can be applied to the polished surface 604b and a pattern can be formed in the reflective layer. For example, a resist layer is applied to layer 608, the resist layer is exposed to radiation of the appropriate wavelength, and the exposed resist layer is etched using any technique apparent to those skilled in the art to form a pattern on layer 608. Can be formed.

  [0095] In one embodiment, a reticle manufacturer may apply a highly reflective layer 608 to the surface 604b of the optical layer 604. However, in a further embodiment, the end user of reticle 600 can apply a highly reflective layer 608 to second surface 604b of optical layer 604 after reticle 600 is delivered to the user. Further, as described above, in one embodiment, the reticle end-user may pattern the highly reflective layer 608 after delivery.

  [0096] FIG. 7 is a flowchart of an exemplary method 700 for generating a reticle, such as reticle 400 of FIGS. 4A and 4B, suitable for use in an EUV lithographic apparatus, according to one embodiment of the invention. In step 702, a conductive material layer, including but not limited to aluminum, is disposed on the first surface of the ultra low expansion (ULE) titanium silicate glass layer. In such embodiments, the thickness of the ULE glass layer is selected such that the thermal resistance of the ULE glass layer is relatively low over the temperature range.

  [0097] In one embodiment, the conductive layer may be disposed on the first surface of the ULE glass layer using any number of deposition techniques that are apparent to those skilled in the art and are suitable for the material. For example, step 702 may place the conductive layer on the first surface of the ULE glass layer using any sputter deposition, spray deposition or physical vapor deposition techniques.

  [0098] The conductive layer disposed on the ULE glass layer is then bonded to the first surface of the cordierite substrate at step 704 to form a reticle. In one embodiment, step 704 anodically bonds the first surface of the cordierite substrate to the conductive layer. However, in further embodiments, the first surface of the cordierite substrate will be apparent to those skilled in the art without departing from the spirit or scope of the present invention, and any number of techniques suitable for cordierite substrates and conductive layers. May be coupled to the conductive layer using or otherwise attached.

  [0099] The second surface of the ULE glass layer is then processed in step 706 to form a substantially flat surface that is substantially free of defects. In one embodiment, the second surface of the ULE glass layer is polished at step 706 to produce a substantially flat and substantially defect free surface. However, in additional or alternative embodiments, the second surface may be treated at step 706 using any technique apparent to those of ordinary skill in the art without departing from the spirit or scope of the present invention.

  [0100] FIG. 8 is a flowchart of an exemplary method 800 for generating a reticle, such as reticle 500 of FIGS. 5A and 5B, suitable for use in an EUV lithographic apparatus, according to one embodiment of the invention. In step 802, the conductive material layer, including but not limited to aluminum, is (i) on the first surface of the ultra-low expansion (ULE) titanium silicate glass layer and (ii) on the first surface of the cordierite substrate. Be placed. In one embodiment, the thickness of the ULE glass (or other optical layer) is selected such that the thermal resistance of the ULE glass (or other optical layer) is relatively low over the applicable temperature range.

  [0101] In one embodiment, the conductive layer is formed on the first surface of the ULE glass layer and on the first surface of the cordierite substrate using any number of deposition techniques that are apparent to those skilled in the art and are suitable for the material. May be arranged. For example, step 802 may place the conductive layer on the ULE glass layer and the first surface of the cordierite substrate using any sputter deposition, spray deposition or physical vapor deposition techniques.

  [0102] The conductive layer disposed on the cordierite substrate is then bonded to the first surface of the zero-dur intermediate layer (eg, layer 530 of FIGS. 5A and 5B) at step 804. Further, at step 806, the conductive layer disposed on the ULE glass layer is then bonded to the second surface of the zero-dur layer, thereby forming a reticle.

  [0103] In one embodiment, one or more conductive layers may be anodically bonded to the respective surfaces of the zero-dur layer in steps 804 and 806. However, in further embodiments, the conductive layer can be formed using any of a number of techniques that are apparent to those skilled in the art without departing from the spirit or scope of the invention and are suitable for cordierite substrates and zero-dur layers. At 806, each surface of the zerodur layer may be bonded or otherwise attached.

  [0104] The second surface of the ULE glass layer is then processed in step 808 to form a substantially flat surface that is substantially free of defects. In one embodiment, the second surface of the ULE glass layer is polished at step 808 to produce a substantially flat and substantially defect free surface. However, in additional or alternative embodiments, the second surface may be processed at step 808 using any other technique that will be apparent to those skilled in the art without departing from the spirit or scope of the present invention.

  [0105] In a further embodiment (not shown), a layer of material that is highly reflective to EUV can be applied to the polished surface of the reticle produced by the exemplary method of FIGS. Further, as will be apparent to those skilled in the art, the pattern may be formed on the applied reflective layer using any number of techniques suitable for reflective materials and EUV lithography processes. For example, the resist layer may be applied to a polished surface, the resist layer is exposed to radiation of the appropriate wavelength, and the exposed resist layer may be etched to form a pattern on the polished surface. it can. In a further embodiment, such additional application and patterning steps can be performed by the reticle manufacturer prior to delivery to the end user. Alternatively, the reticle may be manufactured using the method of FIGS. 7 and 8, and the end user can apply and pattern the reflective coating.

  [0106] As described above with reference to FIGS. 5A and 5, the present invention is not limited to intermediate layers formed from zero-dur. In further embodiments, the intermediate layer has suitable mechanical properties (eg, substantially zero coefficient of thermal expansion over the operating temperature range) and facilitates anodic bonding with the ULE glass layer and cordierite substrate. It can be formed from any number of materials that can be made.

  [0107] In the embodiments described above, the reflective reticle is described in terms of an optical layer formed from ultra low expansion (ULE) titanium silicate glass. However, the optical layer of the present invention is not limited to such materials. In a further embodiment, a reflective reticle described herein has a coefficient of thermal expansion that is substantially zero over an operating temperature range that is characteristic of (i) an EUV lithographic apparatus, and (ii) substantially Can be processed to provide a substantially flat surface free of defects and to follow the application of one or more reflective materials.

  [0108] Furthermore, in the above-described embodiments, the reticle substrate is described with reference to a cordierite ceramic material, but the reticle substrate of the present invention is not limited to such a material. In a further embodiment, the reticle described herein comprises (i) a coefficient of thermal expansion that is substantially zero over an operating temperature range that exhibits the characteristics of the EUV lithographic apparatus, and (ii) relative to that operating range. It may include a substrate formed from any material having a high modulus of elasticity and (iii) a thermal conductivity substantially higher than the thermal conductivity of the optical layer over its operating range.

  [0109] The reflective reticle of the present invention, as described herein throughout its various embodiments, is subject to any pattern error induced by any distortion of the reticle surface due to localized heating from absorbed EUV radiation. Is substantially reduced or eliminated. Any local heating of the optical layer is quickly diffused through the optical layer and into the substrate due to its low thermal resistance. Furthermore, since the thermal conductivity of the substrate is substantially higher than that of the substrate of existing EUV reticles, any local heat flux received by the substrate due to absorption of EUV radiation will diffuse into the substrate and Through and diffuse into a reticle chuck, mask table or other structure supporting the reticle in an EUV lithographic apparatus. Thus, in contrast to the existing EUV reticle shown in FIG. 3, the reticle of the present invention substantially reduces or eliminates thermal distortion of the patterned surface due to absorbed EUV radiation, while being consistent with industry standards. Maintain the thickness of.

Conclusion
[0110] While various embodiments of the present invention have been described above, it should be understood that this embodiment is shown by way of example only and not limitation. It will be apparent to those skilled in the art that various modifications, in form and detail, can be made in the present invention without departing from the spirit and scope of the invention. Accordingly, the breadth and scope of the present invention should not be limited by any of the exemplary embodiments described above, but should be defined only in accordance with the appended claims and their equivalents.

  [0111] Although the summary and summary items of the present invention may describe one or more exemplary embodiments of the invention as contemplated by the inventor (s), all exemplary embodiments are described. It should not be stated, and is therefore not intended to limit the invention and the appended claims in any way.

Claims (15)

An optical layer having a first surface and a second surface;
A substrate, wherein the substrate has a thermal conductivity substantially greater than the thermal conductivity of the optical layer; and
A conductive layer disposed between the optical layer and the substrate, the conductive layer being coupled to one or more of (i) a surface of the substrate and (ii) the first surface of the optical layer. A reticle including a layer. The optical layer comprises a material having a substantially zero coefficient of thermal expansion;
The reticle of claim 1, wherein the substrate comprises a material having a substantially zero coefficient of thermal expansion. The optical layer comprises ultra low expansion (ULE) glass;
The substrate includes cordierite;
The reticle of claim 1, wherein the conductive layer comprises aluminum.   The reticle of claim 1, wherein the conductive layer is disposed on the first surface of the optical layer. A second conductive layer disposed on the surface of the substrate;
An intermediate layer disposed between the conductive layer and the second conductive layer;
The conductive layer is bonded to the first surface of the intermediate layer;
The reticle according to claim 4, wherein the second conductive layer is bonded to a second surface of the intermediate layer.   The reticle of claim 1, wherein the second surface of the optical layer is substantially flat and substantially free of defects.   The reticle of claim 6, further comprising a reflective layer disposed on the second surface of the optical layer.   The reticle of claim 1, wherein the thickness of the substrate is greater than the thickness of the optical layer. An illumination system for generating the radiation beam for a reticle for patterning the radiation beam;
A projection system for projecting a patterned beam onto a target portion of a substrate, comprising:
The reticle is
An optical layer having a first surface and a second surface;
A substrate, wherein the substrate has a thermal conductivity substantially greater than the thermal conductivity of the optical layer; and
A conductive layer disposed between the optical layer and the substrate, the conductive layer being coupled to one or more of (i) a surface of the substrate and (ii) the first surface of the optical layer. A lithographic apparatus comprising: a layer; The optical layer comprises a material having a substantially zero coefficient of thermal expansion;
The lithographic apparatus according to claim 9, wherein the substrate comprises a material having a substantially zero coefficient of thermal expansion. The optical layer comprises ultra low expansion (ULE) glass;
The substrate includes cordierite;
The lithographic apparatus according to claim 9, wherein the conductive layer comprises aluminum.   The lithographic apparatus according to claim 9, wherein the conductive layer is disposed on the first surface of the optical layer. A second conductive layer disposed on the surface of the substrate;
An intermediate layer disposed between the conductive layer and the second conductive layer;
The conductive layer is bonded to the first surface of the intermediate layer;
The lithographic apparatus according to claim 12, wherein the second conductive layer is coupled to a second surface of the intermediate layer. A method of generating a reticle,
Disposing a conductive material layer between the optical layer and a substrate having a thermal conductivity substantially greater than the thermal conductivity of the optical layer, the conductive material layer being on the first surface of the optical layer; Being placed, placing,
And a binding to one of said conductive first surface of the material layer (i) the intermediate layer or (ii) the surface of the substrate, method. The combining is
Bonding the conductive material layer to the first surface of the intermediate layer;
Disposing a second conductive material layer on the surface of the substrate;
The method of claim 14, comprising bonding the second conductive material layer to a second surface of the intermediate layer.

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